This invention relates to the field of medical gas sampling, more particularly for protecting medical gas sampling devices from contamination, obstruction and interfering substances.
Some patients receiving automatic ventilation through an artificial air tube are monitored for respiratory problems by drawing a small sample flow of gas from the air tube and continuously analyzing the level of carbon dioxide (capnography) or other gases. Typically, a sampling tube is connected to the air tube for conveying a sampled flow of gas from the air tube to the gas monitoring equipment, the diameter of the sampling tube being small compared to the diameter of the air tube.
Ventilated patients in the Intensive Care Unit (ICU) commonly have pulmonary problems with many secretions such as copious mucous sputum. These secretions are thixotropic gels which can and do solidify and adhere to a variety of surfaces, including the plastics used in medical tubing and related connectors and adapters used in gas monitoring devices.
In order to draw gas from the air tube, a vacuum is applied to one end of the sampling tube using, for example, a pump in the gas monitoring equipment. This can cause the above mentioned secretions to enter the gas sampling tube and gas monitoring equipment causing inaccurate measurement, or the entrance into the sampling tube can become blocked causing the sample gas flow to stop or become unacceptably low.
Some prior art devices use filtering materials over the sample port hole of airway adapters, but this slows down the sampling process relative to the respiration cycle of the patient.